Pretreatment with bilirubin protects islet against oxidative injury during isolation and purification

A high yield of pure, viable islets is one of the most important prerequisites for successful islet transplantation. However, during isolation and purification, many factors may cause oxidative stress, impacting islet viability. Accumulating evidence indicates that bilirubin (BR) not only has antioxidative but also has cytoprotective activities. In this study, we investigated whether pretreatment with bilirubin would protect islets against oxidative damage during isolation and purification.

Wistar rats were randomly divided into control and BR groups. The latter rats received an injection of BR 2 hours before islet isolation, whereas the controls received vehicle. Islet purity was determined using a dithizone stain. Survival rate and viability were determined using acridine orange and propidium iodide staining and the Cell Counting Kit-8 Kit. Islet function was quantified by testing glucose-stimulated insulin secretion. Islet damage caused by oxidative stress was quantified by measuring the malondialdehyde (MDA) in freshly isolated islets.

Pretreatment with bilirubin did not enhance the purity, but significantly enhanced the survival rate and viability of the islets. Islet function in the BR group was significantly better than that in the control cohort. The MDA level was 0.62 ± 0.23 nmol/L/μg protein in the BR group, which was significantly lower (P < .05) than that in controls (1.31 ± 0.34 nmol/L/μg protein).

We concluded that oxidative stress during islet isolation and purification can be mitigated by BR pretreatment. BR exerts antioxidant and cytoprotective properties by reducing lipid peroxidation (MDA) and enhancing islet viability and function. Pretreatment with BR may become a simple, clinical applicable means to improve human islet isolation and transplantation outcomes.